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84 Cards in this Set
- Front
- Back
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Water molecule is a?
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polar molecule
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Water is the ______ of oxygen?
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Hydride
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The boiling point of water is (group VIA)? same is true for what elements (group VA and VIIA)?
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Much higher than would be predicted from its formula mass, NH3 and HF
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Given the BP of water, what can you predict about hydrides of group 15 and 17 and their boiling points?
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Higher than predicted for their formula mass
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Why do these molecules with such a low molecular mass have such a high boiling point?
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Because they are very polar
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Hydrogen bond is?
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a force of attraction between partial charges, S+ and S-
-individual water molecules attract one another |
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Which molecule usually has the partial positive charge?
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Hydrogen
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Which molecules usually have the partial negative charge?
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O, N, or F
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What type of bond is a hydrogen bond?
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neither an ionic bond or a covalent bond
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The hydrogen bond is a _____ bond.
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weak, only about 5% as strong as a covalent bond
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Because of hydrogen bonds, water has an unusually?
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1. High heat of vaporization (boiling point)
2. High heat of fusion (melting point) 3. High surface tension |
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Liquid water forms a ?
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surface at an interface with air molecules
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What does water do on waxy or greasy surfaces? and why?
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"beads," because wax and grease molecules are nonpolar and do not attract water molecules
-also, water molecules attract themselves much more than they attract nonpolar molecules |
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Why do the water molecules spread out on a clean glass surface though?
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Because the glass has ionic charges present at surface, water is attracted to those sites and spreads out
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What are agents that reduce the surface tension of water?
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surface-active agents or surfactants
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Name some surfactants
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1. soaps and detergents
2. lung surfactant-prevent alveoli from collapsing 3. bile salts- necessary for digestion of fats |
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Water dissolves best those particles that?
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attract water molecules and form "solvent cages"--known as HYDRATION
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Dissolution of ionic compounds happens how?
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water surrounds the ions with hydration shells
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Ionic compounds in which the ions have two or three charges are generally?
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less soluble than those in which the ions are univalent (harder to keep divalent compounds in solutions)
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Dissolution of polar molecules
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the hydration of a polar molecule helps polar molecular substances to dissolve in water
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Hydrates
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water-containing solids
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a hydrate is...
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an ionic compound that incorporates a fixed amount of water molecules in its formula unit
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Water molecules are held within the crystals in? thus, hydrates are?
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Definite proportions
Compounds, not mixtures |
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T or F. Formulas of hydrates are written to show that water is present?
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True
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The water present in a hydrate is referred to as?
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the water of hydration
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Heating the hydrate can expel the water, leaving the ____________ of the substance
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Anhydrous form
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What are dessicants and name some examples?
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Hydrates in their anhydrous forms can be used as drying agents--remove water from air
-silica gel and anhydrous calcium chloride are examples |
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HYGROSCOPIC
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is the general term for any substance that can remove water vapor from air (includes anhydrous forms)
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Name 5 types of solutions
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1. Dilute
2. Concentrated 3. Saturated 4. Supersaturated 5. Unsaturated |
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Dilute
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ratio of solute to solvent is very small
eg, solutions in biological systems |
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Concentrated
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ratio of solute to solvent is large
eg, syrup is a concentrated solution of sugar in water |
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Saturated
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no more solute will dissolve at the given temperature; cooling the solution will normally cause the solute to precipitate
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Supersaturated
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carefully cooling a saturated solution can cause an unstable situation in which more solute than expected is dissolved
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Solubility
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Amound of solute needed to give a saturated solution in a given quantity of solvent at a specific temperature
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Units of solubility
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g solute/ 100 g solvent
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In some cases, a saturated solution may be very?
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Dilute eg, barium sulfate
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In general, solubilities of solids?
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increase with increasing temperature
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Solubilities of gases...
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decrease with increasing temperatures
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Dynamic equilibrium
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a situation in which two opposing events occur at identical rates so that no net change happens in the system
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Example of a dynamic equilibrium
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a system consisting of a saturated solution in contact with excess, undissolved solute
-saturated solution of NaCl in contact with excess, crystalline NaCl. -Rate of ions leaving the crystals and entering the solution is equal to the rate of dissolved ions reforming crystals |
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T or F, in a dynamic equilibrium, the rates of forward and reverse reactions are equal at equilibrium?
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T
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At equilibrium...?
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no net change occurs spontaneously
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What does a forced change (stress) do to the equilibrium?
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upsets the equilibrium
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What can cause stress to the equilibrium?
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Heat
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Heating the system stresses the equilibrium, increasing what?
NaCl + heat --- Na+ + Cl- |
the rate of the forward reaction and causing more NaCl to dissolve
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What happens if the system is maintained at the higher temperature, eventually the rate of the reverse reaction?
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"catches" up and equilibrium is reestablished
-rates of both the forward and reverse reactions are greater than at the lower temperature -no further net change occurs -more ions (Na+, Cl-), less solids NaCl |
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Le Chatlier's Principle
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an equilibrium responds to a forced stress by shifting in the direction that absorbs the stress OR if a system in equilibrium is subjected to a stress (forced change), the system will change in whichever way restores equilibrium
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Application of Le Chatlier's principle to solution of gases involves what Law?
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Henry's
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Henry's Law
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gas(undissolved)---gas dissolved + heat
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Gas solubility decreases with?
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increasing temperature
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How do all gases dissolve ?
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exothermically
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Heating a solution of dissolved gas shifts the above equilibrium?
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to the left
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Some gases dissolve, in part, by reacting chemically with?
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water
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Weight to weight percent (w/w%)
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g solute in 100 g of SOLUTION
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Example of w/w%. a 10% (w/w) glucose solution has 10.0 g of glucose in 100 g of solution, to prepare, dissolve?
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10.0g of glucose in 90.0 g of solvent -- by conservation of mass, the solution weighs 100g
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Is the (w/w%) used in the clincal setting?
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no
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Volume to volume precent (v/v%)
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the number of volumes of a substance present in 100 volumes of mixture
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Example of v/v%
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Air is 21% oxygen- 21 L of oxygen in 100 L of air
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Weight to volume percent (w/v%)
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number of grams of solute in 100mL of solution
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w/v% can also be expressed in?
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g/dL
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Commonly used in the clinical setting, though not a "true" percent because?
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units do no cancel
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Example: 0.9% (w/v) solution of NaCl has 0.9g NaCl per 100mL of solution
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0.9gNaCl/100mL of solution = 9g/L
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100g/100mL = ___% and ratio of ____?
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100%, 1:1 ratio
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2g/100mL = _____% and a ratio of ?
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2%, 1:50
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1g/ 100mL= _______% and a ratio of ?
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1%, 1:100
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Homogenous mixtures
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composition is everywhere the same; a small sample has the same composition and properties of any other sample
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Particles that comprise solutions have formula masses___and diameters of ____?
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no more than a few hundred, 0.1-1nm diameter
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Solutions are usually?
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transparent
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Do solutes separate under the influence of gravity?
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NO
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Colloidal dispersion is what type of mixture?
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homogeneous
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colloidal dispersion particles are? diameters?
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large clusters of ions or are macromolecules (eg, proteins); diameters of 10-200nm
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Tyndall effect
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dispersed particles scatter light; fluid mixture has a milk appearance (albumin)
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Colloidal systems are stable when?
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all of the colloid particles have similar electrical charges
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electrical repulsion prevents?
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aggregation and settling out of solution
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Suspensions are what type of mixture?
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heterogeneous (unless vigorously stirred) - not everywhere the same
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In suspensions, particles are _____ in diameters and ______ separate under the influence of gravity.
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> 1000 nm, readily
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Whole blood is a ?
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suspension
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Whole blood is a suspension, so ____ and ____ suspended in plasma.
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cells, platelets
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Plasma is a ?
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colloidal dispersion- proteins dispersed in plasma water
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Plasma water is an ____ solution, containing many _______ ______.
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aqueous, dissolved substances
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When indivicual water molecules attract one another, what is this force known as?
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a hydrogen bond
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What do surfactants do?
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they interfere with hydrogen bonding which decreases surface tension
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Heating the hydrate can expel the water, leaving what?
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the anhydrous form of the substance
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Drying agents or?
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dessicants
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